1. Department of Prevention and Community Health, Milken Institute School of Public Health, The George Washington University, Washington, DC, USA
2. Department of Health Sciences, University of York, York, USA, Hull York Medical School, York, USA
3. Department of Health Sciences, University of York, York, USA, Usher Institute, University of Edinburgh, Edinburgh, Scotland
4. Centre for Evaluation and Methods, Wolfson Institute of Population Health, Queen Mary University of London, London, UK
5. Department of Health Sciences, University of York, York, USA